Apple Inc. Google Switzerland GmbH Karlstad University University of Aberdeen University of Glasgow This document describes an architecture for exposing transport protocol features to applications for network communication, a Transport Services system. The Transport Services Application Programming Interface (API) is based on an asynchronous, event-driven interaction pattern. This API uses messages for representing data transfer to applications, and describes how implementations can use multiple IP addresses, multiple protocols, and multiple paths, and provide multiple application streams. This document further defines common terminology and concepts to be used in definitions of a Transport Service API and a Transport Services implementation.